Laser Trapping Faux Atoms Creates ‘Super MRI’ Method

Photonics.comFeb 2013
BARCELONA, Spain, Feb. 12, 2013 — A new technique, similar to the MRI but with a much higher resolution and sensitivity, uses artificial atoms to scan individual cells. The findings could revolutionize the field of medical imaging.

Researchers from the Institute of Photonic Sciences (ICFO), in collaboration with the Spanish National Research Council and Macquarie University in Australia, created the “super MRI” method using artificial atoms — diamond nanoparticles doped with nitrogen impurity — to probe very weak magnetic fields such as those generated in some biological molecules.

Conventional MRI techniques register the magnetic fields of atomic nuclei in our bodies, which have been previously excited by an external electromagnetic field. The collective response of all these atoms makes it possible to diagnose and monitor the evolution of certain diseases. However, this technique has a diagnostic resolution on a millimetric scale. Smaller objects do not give enough signal to be measured.

Nanomanipulation of an artificial atom using a laser light trapping technique developed by scientists at ICFO, the Spanish Research Council and Macquarie University. Courtesy of ICFO.
The technique proposed by the group led by Dr. Romain Quidant of ICFO significantly improves the resolution at the nanometer scale, making it possible to measure extremely faint magnetic fields, such as those created by proteins.

“Our approach opens the door for the performance of magnetic resonances on isolated cells, which will offer new sources of information and allow us to better understand the intracellular processes, enabling noninvasive diagnosis,” said Michael Geiselmann, an ICFO researcher who conducted the experiment. Until now, reaching this resolution was possible only in the laboratory using individual atoms at temperatures close to absolute zero.

Individual atoms are highly sensitive to their environment, with a great ability to detect nearby electromagnetic fields. The challenge these atoms present is that they are so small and volatile that, to be manipulated, they must be cooled to temperatures near absolute zero, a complex process that requires an environment so restrictive that it makes individual atoms unviable for potential medical applications.

The artificial atoms used by Quidant and colleagues were formed by a nitrogen impurity captured within a small diamond.

“This impurity has the same sensitivity as an individual atom but is very stable at room temperature due to its encapsulation,” he said. “This diamond shell allows us to handle the nitrogen impurity in a biological environment and, therefore, enables us to scan cells.”

The researchers used laser light to trap and manipulate these artificial atoms. The laser works like tweezers, leading the atoms above the surface of the object to study and extract information from its tiny magnetic fields.

The new technique could revolutionize the field of medical imaging, allowing for substantially higher sensitivity in clinical analysis, an improved capacity for early detection of diseases and, ultimately, a higher probability for successful treatment.

A technique for confining atoms, molecules or small particles within one or more laser beams. This can be accomplished through the use of a single focused beam or multiple intersecting beams. With a single focused beam, the matter is confined to the laser beam's focal area. In the case of multiple intersecting beams, the matter is confined to the area of intersection because of the combined cooling effect of the beams. Also called optical trapping.